This invention relates to the field of Radiology and Orthopedic Surgery. It more particularly relates to x-ray film cassette and leg holders and to a new and improved method of obtaining the axial x-ray view of the knee (patellofemoral joint). This invention allows the patient to be placed supine (face up) on the x-ray table with the knees flexed over the end of the table and the legs supported. The knees are elevated slightly with the adjustment provided to keep the femurs (thigh bones) parallel with the table surface. The x-ray tube and collimator can now be raised over the patient for clearance and the x-ray beam projected downward at an angle. The x-ray film cassette is placed in a holder below the knees and rested on the shins perpendicular to the x-ray beam. The legs are strapped together to control rotation, relax the thigh muscles, and to expose both knees simultaneously. Thus an accurate, reproducible, standardized axial x-ray view of the kneecaps (and patellofemoral joints) is obtained which is comfortable even for the recently injured knee.
So far as is known, this simple Knee Support and Cassette Holder for axial x-rays of the knees described and claimed herein has not been known heretofore. A search of previously issued patents reveals none which relates to the problems encountered in obtaining axial x-ray views of the knee. Furthermore, the closest patents granted discovered in said search relate to an x-ray table (U.S. Pat. No. 1,015,187, Kelly, Jan. 16, 1912), two devices to facilitate x-ray views of the skull (U.S. Pat. No. 2,111,903, Rona, Mar. 22, 1938 and U.S. Pat. No. 2,220,725, Moe, Nov. 5, 1940), and a frame for portable chest x-rays (U.S. Pat. No. 3,705,984, Westenberger, Dec. 12, 1972). None is applicable to the instant invention for knee x-rays.
A search of the medical literature reveals several different methods to obtain axial x-ray views of the kneescaps and patellofermoral joints, all with various deficiencies. The most common technique (Settegast) requires no frame or cassette holder but acutely flexes the knee to obtain the exposure. This draws the kneecap (patella) so far into the intercondylar sulcus that a subluxation (partial dislocation) even if present in slight flexion could not be shown with this view. Also in the event of a recently injured knee it is too painful to acutely flex the knee to obtain this view. Therefore, the axial view is omitted and a fracture or loose bone fragment is occasionally missed. The present invention allows comfortable support of the knee in slight flexion which not only reveals any tendency to slight subluxation of the kneecap but also is the position of maximum comfort for the painful knee.
The modified Jaroschy technique also in current use requires no additional frame or holder and does not require acute flexion of the knee. However, the x-ray beam strikes the x-ray film plane at an angle of 45 degrees causing serious distortion of the image, and the rotation of the legs is not controlled introducing another variable. The present invention obviates these difficulties by holding the x-ray cassette perpendicular to the x-ray beam eliminating distortion, and providing a strap for the legs to control rotation yet allow relaxation.
The method of Brattstrom gives accurate films but is so technically elaborate and complex that it is only applicable for research not clinical use. In addition it utilizes a position of acute flexion incurring the problems mentioned above in reference to the Settegast technique.
The methods of Knuttson and Furmaier have been rendered obsolete by the enlargement of x-ray tubes and collimators over the years. The size of current equipment prevents it from being placed low enough over the patient to make the exposure. The invention described herein flexes the knees over the end of the x-ray table supporting the legs and thus allows the x-ray tube and collimator to be raised clear of the patient for the exposure.